while the FHS does not make /usr/dict illegal, FHS 2.0, section 4.8.1
recommends /usr/share/dict/words. words should be architecture-independent
data, so placing it in /usr/share/ makes sense.
Note that a symlink /usr/dict -> /usr/share/dict would be in compliance
with the FHS (unless you want to classify words as a "large software
package").